The present invention relates to a method and apparatus for building a tobacco filler. More particularly, the invention relates to improvements in a method and apparatus for converting a continuous tobacco stream into a continuous rod-like filler by removing surplus tobacco from the stream.
In a cigarette making machine, a distributor feeds tobacco particles at a rate which is necessary to build a continuous tobacco stream containing a surplus of tobacco, i.e., tobacco in excess of that which is required in the filler of a cigarette rod. This is desirable because the cross-sectional area of the stream varies at an unpredictable rate, i.e., a filler (which is a continuous rod normally containing identical quantities of tobacco in each increment thereof, except when the filler is to be used for the production of dense-end cigarettes) of uniform density can be obtained only if the stream contains a surplus so that the minimum cross-sectional area of each and every portion of the stream is not less than the desired cross-sectional area of the filler.
As a rule, a selected adjustment of the distributor need not be changed if the characteristics of tobacco which is to be converted into a stream and thereupon into a rod-like filler do not change at all or fluctuate within a rather narrow range. For example, if the distributor receives one and the same blend of tobacco whose moisture content is constant, wherein the percentage of ribs, stem and other heavier particles (such particles are normally segregated from the particles which are to form the stream) is constant, and wherein each batch of tobacco particles contains the same or nearly the same amount of so-called shorts and tobacco dust, a selected adjustment of the motor for the distributor need not be changed for extended periods of time, e.g., during an entire shift. However, if the characteristics of tobacco vary considerably from batch to batch or from charge to charge, the selected adjustment might not be satisfactory because the distributor is likely to feed less tobacco than necessary for the making of a satisfactory filler or the stream will contain excessive amounts of surplus tobacco. The latter situation is equally undesirable because the equalizing device or devices invariably produce substantial amounts of so-called short tobacco and tobacco dust as well as because the moisture content of removed surplus tobacco is likely to change during transport back into the magazine of the distributor. Furthermore, the transport of removed surplus tobacco into the magazine of the distributor invariably entails additional comminution of tobacco. Therefore, it is necessary to monitor the quantity of tobacco in successive increments of the filler and to adjust the motor for the moving parts of the distributor when the monitoring step indicates that the tobacco stream should contain larger or smaller quantities of surplus.
Heretofore known apparatus which are used for adjustment of the distributor are not reliable and their reaction to changes in the mass of tobacco in successive increments of the filler is too slow. This is attributable to the nature of detectors which are used for the monitoring operation and also to the fact that presently known monitoring devices cannot transmit signals which are reliable indicators of the monitored mass of tobacco, mainly because the conventional monitoring devices cannot take into consideration unpredictable changes of certain physical and/or chemical characteristics of tobacco particles, especially the moisture content.